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Possible other factor; I've heard the accusation that the CMD/CMB system actually lowers the odds of succeeding on a melee maneuvers in comparison to 3.5E; but I haven't seen a full numbers breakdown (though there exists an optimization by the numbers thread for both 3.5E and Pathfinder (Pathfailure, as people like to call it), so it would be possible to do this relatively easily).
From what I understand, here's the two basic problems w/ the CMB:
(1) CMB includes both stat (typically strength) and size alone w/ base attack bonus. But, base attack bonuses scale much quick for monsters than they do for PCs, i.e., a monster of CR 10 tends to have a BAB of a lot higher than 10, and the rate of that increase only gets steeper as CRs get higher. So, the gap in your check and the monster's check has increased.
(2) The feats that made these checks easier have been nerfed, so that the maneuver is either less effective (trip) or the bonus is less (typically +2 vs +4). The feats stack, though, so you can bring yourself up to the 3.5 standard +4, but you are still missing lots of the other options 3.5 has for improving these checks, such as more unusual feats, magic items, etc.
So, the net result is that it not only takes more resources to get just as good as someone in 3.5 would be, but your relative ranking has gone down. To the point where the builds usually aren't very viable. All that is predicated on the monsters in Pathfinder having analogous stats to the ones in 3.5, but I have seen nothing that would indicate any major change.